The invention relates to a method of operating a motor vehicle, using a driver assistance system to carry out steering interventions.
Such processes are known in the art: In certain driving conditions, for example during parking, maneuvering, or during lane change, additional torque is applied on the steering by electric steering actuators and intended to assist steering motions by the driver. If need be, the steering may also be executed entirely by the driver assistance system, as is known from automatic parking systems.
In order to be able to provide the desired additional steering torque, the electric steering actuator has to consume energy which is drawn from the on-board power supply of the motor vehicle. If the necessary power cannot be made available, steering intervention cannot be executed to the desired extent or even not implemented at all so that control targets cannot be realized by the driver assistance system and comfort may possibly be adversely affected because steering becomes more difficult. EP 1 950 121 A2 discloses therefore to increase the power output of a generator in the on-board power supply in advance of an imminent steering intervention by providing a certain reactive power. When the steering intervention is then executed, the reactive power is dissipated so that the power rise is less as a result of the steering intervention and the driving comfort is improved. Also in this case, there is no guarantee that the required power is fully made available.
In addition to the described demands on the electrical on-board power supply, further operating parameters of the motor vehicle for such steering interventions are of importance. Examples include the ratio of the steering angle at the axles of the motor vehicle. For example, in a driving situation in which the front and rear axles of the motor vehicle are steered in opposite directions, a steering intervention cannot be readily carried out without delay when a steering of the axles in a same direction is required.